Chemisettes were a common accessory in the early nineteenth century. They would fill in the necklines of low-cut dresses, making them suitable for day wear. There were many different styles of Chemisette with some being popular at different times, but the style in the picture above would probably have been popular from about 1805 to 1826 approximately. This one is composed of two hemmed ruffles being finely cartridge pleated at the neck.
The raw edges are covered with linen tape on the inside. The front shoulder seam in this example has small pleats taken in it for decoration.
This chemisette closes at the neck with two cords with tassels at the ends. It also closes with a drawstring in a casing that ties at the waist.
Both chemisettes consist of two front pieces and one back piece that are not joined at the sides. This would be unnecessary as you can only see the part of the chemisette visible at the neck. They are hemmed at the sides and bottom edge.
The other chemisette would be more popular from about 1820 to 1838. It consists of a neckpiece with a ruffle around the edge.
This one has whitework flower embroidery around the edge. Both chemisettes are based off of early nineteenth-century examples in the UK National Trust and can be found in Patterns of Fashion 1, with a pattern taken from the originals. By the 1850s necklines had become higher in the daytime and there was no longer any need to wear a chemisette. They fell away from popular fashion, though smaller decorative collars started becoming fashionable at that time.